1. Field of the Invention
The present invention relates in general to the dynamic configuration of telecommunications networks, particularly cellular mobile radio communications networks (hereinafter also referred to as cellular networks, for conciseness). More specifically, the invention relates to the dynamic configuration of base radio stations of a cellular network.
2. Description of the Related Art
As known, in the context of cellular networks, the exchange of communications in transmission and reception (between a transmitter and a receiver) occurs through radio communications that use respective communication radio channels. In the context of the present description, the term “radio channel” is used for designating the physical resource that univocally identifies the radio connection between a transmitter and a receiver in the cellular network; the radio channel can be of different types, depending on the access technique and the type of system or network.
For example, in the FDMA (Frequency Division Multiple Access) access technique, the radio channel is identified by its frequency; in the TDMA (Time Division Multiple Access) access technique, the radio channel is identified by a time slot; in the CDMA (Code Division Multiple Access) access technique, the radio channel is identified by a code, for example of the orthogonal type. Two or more access techniques can also be combined: in such a case, the radio channel is identified by the characteristic elements of each of the combined access techniques; for example in the GSM (Global System for Mobile communication) system, that, as known, uses a combined FDMA/TDMA access technique, the radio channel is identified by the frequency and time slot pair.
In the context of the present description, the term “system” or “radio system” is used to identify a plurality of elements in a communications network that are mutually coordinated according to a determined criterion or set of criteria (namely a “standard”).
The terms “GSM system”, “GPRS (General Packet Radio Service) system”, “EDGE (Enhanced Data rates for Global Evolution) system”, “UMTS (Universal Mobile Telecommunication System) system”, “WLAN (Wireless Local Area Network) system” are therefore used to identify the plurality of elements in a communications network related to the corresponding standard.
Cellular networks generally comprise a radio access network and a core network.
The radio access network in turn comprises a plurality of base radio stations, each one adapted to manage one or more cells, and a number of radio control nodes or radio controllers adapted to manage one or more base radio stations.
Depending on the system, the base radio stations take different denominations, being called “BTS” (Base Transceiver Station) in the GSM/GPRS/EDGE system or the 802.16 (WIMAX) system, “NodeB” (Node Base) in the UMTS system, “Access Point” in WLAN (802.11x) systems, while the corresponding radio control nodes or radio controllers are defined as “BSC” (Base Station Controller) in the GSM/GPRS/EDGE, and RNC (Radio Network Controller) in the UMTS system.
The core network comprises core network elements or nodes that have various names, for example “MSC” (Mobile Switching Center), “SGSN” (Serving GPRS Support Node) and “GGSN” (Gateway GPRS Support Node).
In general, the elements composing the radio access network are specific to the cellular system they belong to (for example, BTS and BSC in GSM/GPRS/EDGE systems, NodeB and RNC in UMTS systems) and are not interchangeable among the different systems. The core-network elements, instead, can be used for governing and managing multiple standards or types of systems.
From the hardware viewpoint, every base radio station (shortly, base station) is able to manage a maximum number of radio resources related to the system for which it has been designed, depending on the complexity and amount of hardware it has been equipped with.
In particular, in every base station, the receiving-transmitting capacity can be changed, by increasing or decreasing the number of hardware resources (e.g., transceivers), statically and a posteriori, on the basis of network traffic measurements and consequent cellular re-planning.
The development of different systems that temporally and geographically coexist (in a shared area) poses the technical problem of simultaneously managing in the same area two or more systems so as to make the network meet users' characteristics and optimise the use of resources. Typically, such kind of problem occurs for a radio-mobile network operator or manager that already has a deployed network and wants to add thereto a network compliant to a new-generation system (for example an operator having a GSM/GPRS/EDGE network deployed in the field may wish to add a UMTS network).
In addition to the problem of installing new hardware components and make them coexist with the already existing ones, the network manager may wish to be able to dynamically manage the hardware resources dedicated to the system already deployed and to the new-generation system, depending on the changes in time of the traffic in the cells of the area of interest.
In the art it has been proposed that the operators that in the past installed a second-generation cellular network (e.g., compliant to the GSM/GPRS/EDGE or IS-95—Interim Standard 95), in order to be able to deploy third-generation networks (e.g. UMTS or CDMA 2000—Code Division Multiple Access 2000), shall install completely new hardware elements, particularly base radio stations (NodeB) and radio controllers (RNC).
For example, Flavio Muratore et al., in “UMTS—Mobile Communications for the Future”, John Wiley & Sons Ltd., 2001, Chapter 2, dedicated to UMTS, suggest to share the core network part and install a completely new access network uncoupled from the already present access network; in this case, balancing between access networks can only occur by means of physical hardware modification interventions (addition or removal of available resources).
This kind of solution is costly and does not allow a dynamic resources management. Actually, although second- and third-generation base stations are often mutually co-located, radio access networks nodes belonging to different systems are completely uncoupled and independent from one another.
Systems are also known wherein the access network (intended as comprised of mobile terminals, base stations, network nodes and the like) have reconfigurable elements (apparatus and/or devices), as for example disclosed in J. Mitola, “The Software Radio Architecture”, IEEE Communications Magazine, May 1995, and E. Buracchini “The Software Radio Concept”, IEEE Communications Magazine, September 2000. These reconfigurable systems comprise apparatuses and/or devices whose operation can be reconfigured when desired: for example, a reconfigurable mobile terminal adapted to operate in a second-generation system (e.g., in a GSM/GPRS/EDGE network), can be reconfigured to become able to operate in a third-generation system (e.g., in a UMTS or CDMA 2000 network), or in a WLAN system, or in a DVB-T (Digital Video Broadcasting Terrestrial) system, etc.
In order to be able to configure or reconfigure an apparatus or device, its operating functions have to be implemented by means of a technology that is in turn able to be configured or reconfigured; therefore, reconfigurable devices have a reprogrammable hardware consisting of a set of FPGAs (Field Programmable Gate Arrays), DSPs (Digital Signal Processors) and microprocessors, and the individual device functionalities, even at a lower protocol level, are implemented in software. Consequently, in order to reconfigure such an apparatus it is in general sufficient to replace the operating software that manages the device hardware.
Documents U.S. Pat. No. 5,592,480 and U.S. Pat. No. 6,011,785 describe how to realise a base station of the access network with reconfigurable hardware, that is able to support a plurality of mobile radio system and share processing resources among them. In particular, these documents disclose the architecture of a reconfigurable base station that is able to support many cellular systems and to reconfigure hardware resources depending on the type of traffic in the cells covered by the base station. The reconfigurable base station is realised with reconfigurable hardware using DSPs that allow using several standardised radio interfaces by dynamically redistributing the resources inside the cells. The hardware resources reconfiguration occurs autonomously by the base station itself, that is able to configure or reconfigure itself depending on the traffic in the cells covered by the base station.
When a sufficiently wide set of cells in a certain area (e.g. a town or its centre) is considered, the traffic, generated by one or more different systems, may change even significantly in different hours of the day.
It may also occur that, in some areas (called “hot spots”) where the traffic is heavier, one or more congested cells exist, experiencing a high degree of calls/connections blocks, while nearby cells are scarcely loaded or experience low calls/connections blocks percentages.
Document U.S. Pat. No. 6,894,431 discloses, in the context of reconfigurable cellular networks, a method for reconfiguring a cell of a radio system taking into account the co-channel interference. The method is applicable only to cells belonging to a same BTS of a same radio system. The BTS hardware resources can be assigned based on the traffic requirements, proportionally to the traffic demand, among different sectors of a same BTS. The co-channel interference is only evaluated in respect with cells of a same BTS.
Document US 2005/197135 discloses a base station node that includes a radio frequency (RF) monitor and at least one signal processor. The RF monitor is operable to monitor traffic associated with a plurality of wireless communication devices to determine at least one requested load having a corresponding air interface standard. The signal processor is coupled to the RF monitor and is operable to be dynamically reconfigured to support the air interface standard corresponding to the requested load.
Document WO 2006/064302 describes a reconfigurable network architecture capable of adapting to changes in the traffic in respect of one or more radio systems present in a service area, and particularly capable of dynamically reducing calls/connections blocks due to a congestion of at least one cell of a base station, taking into account parameters useful to guarantee the quality of service. The resources that are considered for increasing/reducing the network capacity are the frequencies, both for GSM and for UMTS systems. The capacity of a cell is increased by adding one or more carriers, and it is decreased by eliminating them.
The reconfigurable network architecture allows to dynamically reduce the blockage of a cell or a set of cells managed by a base station and including one or more systems, without recurring, for example, to the addition of further base stations.